Newly Developed Resorbable Magnesium Biomaterials for Orbital Floor Reconstruction in Caprine and Ovine Animal Models-A Prototype Design and Proof-of-Principle Study.

BACKGROUND: orbital floor fractures have not been reconstructed using magnesium biomaterials. METHODS: To test technical feasibility, ex vivo caprine and ovine heads (n = 5) were used. Head tissues were harvested from pubescent animals (n = 5; mean age: 3.2 years; mean mass: 26.3 kg) and stored below 11 degrees for 7-10 days. All procedures were performed in a university animal resource facility. Two experienced maxillofacial surgeons performed orbital floor procedures in both orbits of all animals in a step-by-step preplanned dissection. A transconjunctival approach was chosen to repair the orbital floor with three different implants (i.e., magnesium implants; titanium mesh; and polydioxanone or PDO sheets). The position of each implant was evaluated by Cone-beam computed tomography (CBCT). RESULTS: Axial, coronal, and sagittal plane images showed good positioning of the magnesium plates. The magnesium plates had a radiographic visibility similar to that of the PDO sheets but lower than that of the titanium mesh. CONCLUSIONS: The prototype design study showed a novel indication for magnesium biomaterials. Further testing of this new biomaterial may lead to the first resorbable biomaterial with good mechanical properties for extensive orbital wall defects.

Degradation behavior and osseointegration of Mg-Zn-Ca screws in different bone regions of growing sheep: a pilot study.

Magnesium (Mg)-based implants are highly attractive for the orthopedic field and may replace titanium (Ti) as support for fracture healing. To determine the implant-bone interaction in different bony regions, we implanted Mg-based alloy ZX00 (Mg < 0.5 Zn < 0.5 Ca, in wt%) and Ti-screws into the distal epiphysis and distal metaphysis of sheep tibiae. The implant degradation and osseointegration were assessed in vivo and ex vivo after 4, 6 and 12 weeks, using a combination of clinical computed tomography, medium-resolution micro computed tomography (µCT) and high-resolution synchrotron radiation µCT (SRµCT). Implant volume loss, gas formation and bone growth were evaluated for both implantation sites and each bone region independently. Additionally, histological analysis of bone growth was performed on embedded hard-tissue samples. We demonstrate that in all cases, the degradation rate of ZX00-implants ranges between 0.23 and 0.75 mm/year. The highest degradation rates were found in the epiphysis. Bone-to-implant contact varied between the time points and bone types for both materials. Mostly, bone-volume-to-total-volume was higher around Ti-implants. However, we found an increased cortical thickness around the ZX00-screws when compared with the Ti-screws. Our results showed the suitability of ZX00-screws for implantation into the distal meta- and epiphysis.

Influence of high-pressure torsion deformation on the corrosion behaviour of a bioresorbable Mg-based alloy studied by positron annihilation.

The effect of high-pressure torsion (HPT) on the corrosion behavior of extruded ZX00 (Mg-0.45wt%Zn-0.45wt%Ca) in phosphate buffered saline solution is investigated. MgCaZn alloys are promising candidates for the use as bioresorbable implant materials and, therefore, are in the focus of current research. To improve their strength, severe plastic deformation, e.g. via the technique of HPT, can be used. Positron lifetime spectroscopy (PLS) is applied as sensitive tool for studying open-volume defects which evolve during HPT processing and subsequent corrosion. The studies were complemented by electrochemical impedance spectroscopy (EIS). In the uncorroded state, grain boundaries are the major type of positron trap as quantitatively analysed by means of diffusion-reaction models for positron trapping and annihilation in fine-grained alloys. Upon corrosion, positronium formation and annihilation indicate larger open-volume structures, such as pores and cracks, in the emerging corrosion product and oxide layers. Both PLS and EIS clearly show that HPT-deformation strongly reduces the resistance against corrosion. Evidence is found for corrosion-induced open-volume defects, presumably related to hydrogen, in deeper parts of the material below the corrosion layer.

A 3-Dimensional In Vitro Model of Zonally Organized Extracellular Matrix.

OBJECTIVE: Functional cartilage repair requires the new formation of organized hyaline cartilaginous matrix to avoid the generation of fibrous repair tissue. The potential of mesenchymal progenitors was used to assemble a 3-dimensional structure in vitro, reflecting the zonation of collagen matrix in hyaline articular cartilage. DESIGN: The 3-dimensional architecture of collagen alignment in pellet cultures of chondroprogenitors (CPs) was assessed with Picrosirius red staining analyzed under polarized light. In parallel assays, the trilineage capability was confirmed by calcium deposition during osteogenesis by alizarin S staining and alkaline phosphatase staining. Using reverse transcription-quantitative polymerase chain reaction (RT-qPCR), mRNA levels of ALP, RUNX2, and BGLAP were assessed after 21 days of osteoinduction. Lipid droplets were stained with oil red O and adipogenic differentiation was confirmed by RT-qPCR analysis of PPARG and LPL gene expression. RESULTS: Under conditions promoting the chondrogenic signature in self-assembling constructs, CPs formed an aligned extracellular matrix, positive for glycosaminoglycans and collagen type II, showing developing zonation of birefringent collagen fibers along the cross section of pellets, which reflect the distribution of collagen fibers in hyaline cartilage. Induced osteogenic and adipogenic differentiation confirmed the trilineage potential of CPs. CONCLUSION: This model promotes the differentiation and self-organization of postnatal chondroprogenitors, resulting in the formation of zonally organized engineered hyaline cartilage comparable to the 3 zones of native cartilage.

A lean magnesium-zinc-calcium alloy ZX00 used for bone fracture stabilization in a large growing-animal model.

Over the last decade, demand has increased for developing new, alternative materials in pediatric trauma care to overcome the disadvantages associated with conventional implant materials. Magnesium (Mg)-based alloys seem to adequately fulfill the vision of a homogeneously resorbable, biocompatible, load-bearing and functionally supportive implant. The aim of the present study is to introduce the high-strength, lean alloy Mg‒0.45Zn‒0.45Ca, in wt% (ZX00), and for the first time investigate the clinical applicability of screw osteosynthesis using this alloy that contains no rare-earth elements. The alloy was applied in a growing sheep model with osteotomized bone (simulating a fracture) and compared to a non-osteotomy control group regarding degradation behavior and fracture healing. The alloy exhibits an ultimate tensile strength of 285.7 ± 3.1 MPa, an elongation at fracture of 18.2 ± 2.1%, and a reduced in vitro degradation rate compared to alloys containing higher amounts of Zn. In vivo, no significant difference between the osteotomized bone and the control group was found regarding the change in screw volume over implantation time. Therefore, it can be concluded that the fracture healing process, including its effects on the surrounding area, has no significant influence on degradation behavior. There was also no negative influence from hydrogen-gas formation on fracture healing. Despite the proximal and distal screws showing chronologically different gas release, the osteotomy showed complete consolidation. STATEMENT OF SIGNIFICANCE: Conventional implants involve several disadvantages in pediatric trauma care. Magnesium-based alloys seem to overcome these issues as discussed in the recent literature. This study evaluates the clinical applicability of high-strength lean Mg‒0.45Zn‒0.45Ca (ZX00) screws in a growing-sheep model. Two groups, one including a simulated fracture and one group without fracture, underwent implantation of the alloy and were compared to each other. No significant difference regarding screw volume was observed between the groups. There was no negative influence of hydrogen-gas formation on fracture healing and a complete fracture consolidation was found after 12 weeks for all animals investigated.

[Supracondylar humeral fractures in childhood]. / Suprakondyläre Humerusfraktur im Kindesalter.

The classification of supracondylar humeral fractures in German-speaking areas is carried out according to von Laer, which has been appropriated from the AO system and has the advantage that it can be used to derive the treatment. When indicated immediate surgery is given preference over a delayed treatment. The result is controlled by functional tests directly during the operation. Instability of the fracture and correct placement of the Kirschner (K) wires are challenging. Alternatives are an external fixator and elastically stable intramedullary nailing (ESIN). Concomitant injuries initially affect the median nerve and the brachial artery and secondarily the radial nerve. Lesions of the ulnar nerve are mostly a postoperative complication. The bony consolidation is achieved after 3-4 weeks and afterwards implant removal can be safely carried out. Embedded K­wires and ESIN are removed after 3-6 months, depending on the surgical capacity and complaints of the patient.

A 300 µm Organotypic Bone Slice Culture Model for Temporal Investigation of Endochondral Osteogenesis.

Translational studies to elucidate the response of immature bone to biologic and physical stimuli have been held back by the lack of a viable long-term functional bone explant model. This study attempts to bridge this gap between cell culture and animal model studies. In this study, we describe a methodology to derive a 300 µm organotypic femur slice comprising physiological zones (epiphysis and meta-diaphysis) essential for endochondral bone development. The unique capability of slice culture model incorporating enhanced nutrient access to distinct bone tissue components associated with linear bone growth facilitates the investigation of the orchestrated cellular transition of chondrogenic and osteogenic cells involved in endochondral bone development in an ex vivo setup. Bone slices of 300 µm were prepared from 4-day-old postnatal rats and were viable in culture up to 21 days. On days 7 and 15, an increase in chondrogenic and osteogenic modulations was confirmed in epiphysis, metaphysis, and diaphysis. An increase in osteocytes, osteoblasts, and hypertrophic cells were found at these time points, as well as a noticeable increased expression of chondrogenic and osteogenic markers (collagen II, Runx2, and osteocalcin) confirmed endochondral progression. Osteoclast-mediated bone resorption was demonstrated on day 15 by tartrate-resistant acid phosphatase staining. Attenuated total reflection infrared spectroscopic analyses, furthermore, confirmed a time-dependent increase in phosphate levels, bone minerals, and hydroxyapatite for 15 days. Our establishment of a bone slice culture model closely mimicking the in vivo cellular transitions and endochondral microenvironment of a mineralizing bone provides a vital new tool for the elucidation of cellular and endochondral mechanisms of bone development, maturation, and growth plate modulations. The presented model has the potential to be utilized in implementation of preclinical, toxicological, and therapeutic investigations.

Resorbable implants in pediatric fracture treatment.

Pediatric osteosynthesis has developed over the last 20 years, thereby reducing medical and economic burden, including long and expensive hospitalization. Currently, conventional and rigid alloying systems such as titanium are used for stabilization of bone fractures in children. In many cases, implants must be removed, as otherwise growth would be impeded. Biodegradable implant materials exhibit beneficial properties and would make a second removal surgery unnecessary. In the following article, we will give an overview of implant materials that are currently used in pediatric traumatology with a focus on Mg-based implants. Furthermore, we will discuss current scientific knowledge on resorbable implants, including results from pre-clinics and clinics.

Assessment of pharmacokinetics for microvessel proliferation by DCE-MRI for early detection of physeal bone bridge formation in an animal model.

OBJECTIVES: Bone bridge formation occurs after physeal lesions and can lead to growth arrest if not reversed. Previous investigations on the underlying mechanisms of this formation used histological methods. Therefore, this study aimed to apply a minimally invasive method using dynamic contrast-enhanced MRI (DCE-MRI). MATERIALS AND METHODS: Changes in functional parameters related to the microvessel system were assessed in a longitudinal study of a cohort of an animal model applying a reference region model. The development of morphology of the injured physis was investigated with 3D high-resolution MRI. To acquire complementary information for MRI-related findings qRT-PCR and immunohistochemical data were acquired for a second cohort of the animal model. RESULTS: The evaluation of the pharmacokinetic parameters showed a first rise of the transfer coefficient 7 days post-lesion and a maximum 42 days after operation. The analysis of the complementary data showed a connection of the first rise to microvessel proliferation while the maximum value was linked to bone remodeling. CONCLUSION: The pharmacokinetic analysis of DCE-MRI provides information on a proliferation of microvessels during the healing process as a sign for bone bridge formation. Thereby, DCE-MRI could identify details, which up to now required analyses of highly invasive methods.

Gadolinium accumulation in organs of Sprague-Dawley® rats after implantation of a biodegradable magnesium-gadolinium alloy.

Biodegradable magnesium implants are under investigation because of their promising properties as medical devices. For enhancing the mechanical properties and the degradation resistance, rare earth elements are often used as alloying elements. In this study Mg10Gd pins were implanted into Sprague-Dawley® rats. The pin volume loss and a possible accumulation of magnesium and gadolinium in the rats' organs and blood were investigated in a long-term study over 36weeks. The results showed that Mg10Gd is a fast disintegrating material. Already 12weeks after implantation the alloy is fragmented to smaller particles, which can be found within the intramedullary cavity and the cortical bones. They disturbed the bone remodeling until the end of the study. The results concerning the elements' distribution in the animals' bodies were even more striking, since an accumulation of gadolinium could be observed in the investigated organs over the whole time span. The most affected tissue was the spleen, with up to 3240µgGd/kg wet mass, followed by the lung, liver and kidney (up to 1040, 685 and 207µgGd/kg). In the brain, muscle and heart, the gadolinium concentrations were much smaller (less than 20µg/kg), but an accumulation could still be detected. Interestingly, blood serum samples showed no accumulation of magnesium and gadolinium. This is the first time that an accumulation of gadolinium in animal organs was observed after the application of a gadolinium-containing degradable magnesium implant. These findings demonstrate the importance of future investigations concerning the distribution of the constituents of new biodegradable materials in the body, to ensure the patients' safety. STATEMENT OF SIGNIFICANCE: In the last years, biodegradable Mg alloys are under investigation due to their promising properties as orthopaedic devices used for bone fracture stabilization. Gadolinium as Rare Earth Element enhances the mechanical properties of Mg-Gd alloys but its toxicity in humans is still questionable. Up to now, there is no study investigating the elements' metabolism of a REE-containing Magnesium alloy in an animal model. In this study, we examined the gadolinium distribution and accumulation in rat organs during the degradation of Mg10Gd. Our findings showed that Gd is accumulating in the animal organs, especially in spleen, liver and kidney. This study is of crucial benefit regarding a safe application of REE-containing Magnesium alloys in humans.

Advanced interlocking systems to improve heavy-load-bearing characteristics of flexible intramedullary nailing.

Flexible intramedullary nailing (FIN) is a minimally invasive and widespread standard method for osteosynthesis of pediatric long bone fractures. In the case of unstable fractures of the lower extremity, interlocking systems need to be used to prevent axial shortening and subsequent perforation of the nail at its insertion site. In the present study, four different screw-fixed interlocking systems for FINs (Hofer TwinPlug with two 3-mm titanium interlocking screws, Hofer FixPlug with 3-mm titanium interlocking screw, Hofer Plug with 3.5-mm titanium interlocking screw, and Hofer Plug with 3-mm titanium interlocking screw) in comparison with the commonly used Ender stainless steel nails (locked with 3.5-mm screw) were experimentally investigated in cadaveric lamb tibiae, regarding their load characteristics and failure modes in the case of heavy loading. The specimens were subjected to sequential axial cyclic loading of 5000cycles with stepwise increase of the load amplitude until failure. Migration of locking screws and internal damage of bone tissue was quantified by micro-computed tomography (CT) imaging. Ender nails failed on average at a peak load of 800 N, TwinPlugs at 1367 N, FixPlugs at 1222 N, Plugs 3.5mm at 1225 N and Plugs 3.0mm at 971 N. TwinPlugs, FixPlugs, and Plugs 3.5mm failed in a slow manner over several hundred loading cycles, whereas Ender nails and Plugs 3.0mm exhibited abrupt failure without any prior indication. Our results confirm that axial stability of FIN can be further improved by screw-fixed plugs by simultaneously avoiding shortcomings of an eye-locked system, which the Ender nails are. Considering biomechanical results, plug interlocking systems with 3.5-mm screws should be favored over conventional Ender nails and plugs with 3-mm screws.

Effects of Corroded and Non-Corroded Biodegradable Mg and Mg Alloys on Viability, Morphology and Differentiation of MC3T3-E1 Cells Elicited by Direct Cell/Material Interaction.

This study investigated the effect of biodegradable Mg and Mg alloys on selected properties of MC3T3-E1 cells elicited by direct cell/material interaction. The chemical composition and morphology of the surface of Mg and Mg based alloys (Mg2Ag and Mg10Gd) were analysed by scanning electron microscopy (SEM) and EDX, following corrosion in cell culture medium for 1, 2, 3 and 8 days. The most pronounced difference in surface morphology, namely crystal formation, was observed when Pure Mg and Mg2Ag were immersed in cell medium for 8 days, and was associated with an increase in atomic % of oxygen and a decrease of surface calcium and phosphorous. Crystal formation on the surface of Mg10Gd was, in contrast, negligible at all time points. Time-dependent changes in oxygen, calcium and phosphorous surface content were furthermore not observed for Mg10Gd. MC3T3-E1 cell viability was reduced by culture on the surfaces of corroded Mg, Mg2Ag and Mg10Gd in a corrosion time-independent manner. Cells did not survive when cultured on 3 day pre-corroded Pure Mg and Mg2Ag, indicating crystal formation to be particular detrimental in this regard. Cell viability was not affected when cells were cultured on non-corroded Mg and Mg alloys for up to 12 days. These results suggest that corrosion associated changes in surface morphology and chemical composition significantly hamper cell viability and, thus, that non-corroded surfaces are more conducive to cell survival. An analysis of the differentiation potential of MC3T3-E1 cells cultured on non-corroded samples based on measurement of Collagen I and Runx2 expression, revealed a down-regulation of these markers within the first 6 days following cell seeding on all samples, despite persistent survival and proliferation. Cells cultured on Mg10Gd, however, exhibited a pronounced upregulation of collagen I and Runx2 between days 8 and 12, indicating an enhancement of osteointegration by this alloy that could be valuable for in vivo orthopedic applications.

Clinical impact of interleukin 6 as a predictive biomarker in the early diagnosis of postoperative systemic inflammatory response syndrome after major thoracic surgery: A prospective clinical trial.

BACKGROUND: Postoperative systemic inflammatory response syndrome and sepsis are associated with high morbidity and mortality rates. Early detection of postoperative systemic inflammatory response syndrome improves the outcome. The aim of this study was to evaluate the feasibility of interleukin 6 as a predictive biomarker in the early diagnosis of postoperative systemic inflammatory response syndrome after a major thoracic operation. METHODS: A total of 94 patients were enrolled in this prospective, clinical, single-center study. The enrolled subjects underwent either lung resection or esophageal operation. Interleukin 6, procalcitonin, C-reactive protein, and leucocytes were measured sequentially before, during, and after the operation. These levels were compared between patients who developed postoperative systemic inflammatory response syndrome and those who did not. RESULTS: The enrollees who completed the study included of 55 males (79.7%) and 14 females (20.3%) with a mean age of 60.9 years. Twenty patients (29.0%) developed systemic inflammatory response syndrome at a median time of 33.0 hours postoperatively. In cases of postoperative systemic inflammatory response syndrome, interleukin 6 was the most predictive biomarker, showing a striking increase on the day of operation and preceding the median onset of postoperative systemic inflammatory response syndrome, which occurred the next day (P ≤ .001). Peak procalcitonin and C-reactive protein occurrence were significantly delayed at 24 hours (P = .012) and 48 hours (P = .012). There was no mortality 30 days postoperatively. CONCLUSION: Interleukin 6 is a reliable predictor of postoperative systemic inflammatory response syndrome, and it is able to detect postoperative system inflammatory response syndrome before the onset of related clinical symptoms. When identifying patients at high risk, it would be beneficial to include interleukin 6 in conventional postoperative monitoring, particularly after extended surgical resection.

In vitro and in vivo comparison of binary Mg alloys and pure Mg.

Biodegradable materials are under investigation due to their promising properties for biomedical applications as implant material. In the present study, two binary magnesium (Mg) alloys (Mg2Ag and Mg10Gd) and pure Mg (99.99%) were used in order to compare the degradation performance of the materials in in vitro to in vivo conditions. In vitro analysis of cell distribution and viability was performed on discs of pure Mg, Mg2Ag and Mg10Gd. The results verified viable pre-osteoblast cells on all three alloys and no obvious toxic effect within the first two weeks. The degradation rates in in vitro and in vivo conditions (Sprague-Dawley® rats) showed that the degradation rates differ especially in the 1st week of the experiments. While in vitro Mg2Ag displayed the fastest degradation rate, in vivo, Mg10Gd revealed the highest degradation rate. After four weeks of in vitro immersion tests, the degradation rate of Mg2Ag was significantly reduced and approached the values of pure Mg and Mg10Gd. Interestingly, after 4 weeks the estimated in vitro degradation rates approximate in vivo values. Our systematic experiment indicates that a correlation between in vitro and in vivo observations still has some limitations that have to be considered in order to perform representative in vitro experiments that display the in vivo situation.

The origin points of the knee collateral ligaments: an MRI study on paediatric patients during growth.

PURPOSE: Different femoral origins for both the medial collateral ligament (MCL) and the lateral collateral ligament (LCL) have been reported in the growing skeleton (epiphyseal and metaphyseal). Knowledge about the exact attachment sites is mandatory for anatomically correct reconstruction. This study assesses the femoral origins of the knee collateral ligaments in skeletally immature individuals using magnetic resonance imaging (MRI). METHODS: MRIs of 336 knee joints (median age 15 years (range 2-18 years), m = 209 and f = 127) were retrospectively analysed to assess the distances between the femoral origins of the MCL and LCL to the distal femoral growth plate. In 175 patients, the body sizes were additionally retrieved from medical records. RESULTS: Both MCL and LCL ligament origins were invariably located on the epiphysis. Mean MCL origin-growth plate distance was 9.6 mm (SD 2.1 mm; range 2.2-13.6 mm) in boys and 8.6 mm (SD 1.5 mm; range 3.4-12.0 mm) in girls. Mean LCL origin-growth plate distance was 9.3 mm (SD 1.8 mm; range 4.3-13.0 mm) in boys and 8.2 mm (SD 1.5 mm; range 3.4-11.8 mm) in girls. The distance between the growth plate and both collateral ligaments as well as the length of the LCL correlated positively with patients' age and body size (MCL R(2) = 0.673 and 0.556, LCL R (2) = 0.734 and 0.645, LCL length R(2) = 0.589 and 0.741; all p < 0.001). CONCLUSIONS: During growth, the femoral origins of the MCL and the LCL are constantly located on the distal femoral epiphysis. There is a linear increase in the distances from the ligaments' origins to the growth plate according to age and body size. This new information may be of clinical importance for reconstructive surgery of the knee's collateral ligaments.

Biomarkers of Chondrocyte Apoptosis and Autophagy in Osteoarthritis.

Cell death with morphological and molecular features of apoptosis has been detected in osteoarthritic (OA) cartilage, which suggests a key role for chondrocyte death/survival in the pathogenesis of OA. Identification of biomarkers of chondrocyte apoptosis may facilitate the development of novel therapies that may eliminate the cause or, at least, slow down the degenerative processes in OA. The aim of this review was to explore the molecular markers and signals that induce chondrocyte apoptosis in OA. A literature search was conducted in PubMed, Scopus, Web of Science and Google Scholar using the keywords chondrocyte death, apoptosis, osteoarthritis, autophagy and biomarker. Several molecules considered to be markers of chondrocyte apoptosis will be discussed in this brief review. Molecular markers and signalling pathways associated with chondroycte apoptosis may turn out to be therapeutic targets in OA and approaches aimed at neutralizing apoptosis-inducing molecules may at least delay the progression of cartilage degeneration in OA.

Unlocked and locked elastic stable intramedullary nailing in an ovine tibia fracture model: a biomechanical study.

In the present study, four different systems of elastic stable intramedullary nails (unlocked, Ender stainless steel nails locked with 3-mm screws, titanium nails locked with end caps, titanium nails locked with plugs and 3-mm screws) were implanted in cadaveric ovine tibiae. Fractures were simulated by a transverse diaphyseal osteotomy. The specimens were subjected to simultaneous axial and torsional fatigue loading of 5000 and 1000 cycles, respectively. The unlocked systems failed at an axial load of 200 N peak amplitude. End caps systems withstood axial loads up to 800 N for 1000 cycles, and ender nails and plugs lasted up to 1000 N for 1000 cycles. All systems showed a decrease of axial stiffness with higher loads and endured cycles. Ender nails and nails locked with plugs failed by penetration of the distal epiphysis rather than by loosening of the interlocking system. Overall, the titanium nails locked with plugs and 3-mm screws exhibited superior test results.